The invention relates to a front attachment for harvesting corn for a self-propelled combine harvester. The inventive front attachment comprises harvesting devices for grasping and guiding the corn stalks, for picking the corn cobs and for conveying the picked corn cobs. In particular, the front attachment has intake conveyor mechanisms extending across the width thereof and snapping units, which are disposed downstream of the intake conveyor mechanisms in the direction of the crop flow and substantially comprise snapping rollers rotating opposite to direction of travel. The front attachment also has a cross conveyor equipped with opposing auger sections, by means of which harvested corn cobs can be drawn together in the center of the front attachment and fed from there to a feed rake. The intake conveyor mechanisms and/or the snapping rollers and/or the cross conveyor are driven via at least one driven mechanism of the combine harvester.
Corn, as a root crop, is generally cultivated in rows located approximately 75 cm apart, wherein sowing is carried out by sowing individual seeds. Corn plants that have gone to seed reach a height of up to three meters. The corn plant substantially comprises a corn stalk, corn leaves having a length of up to one meter and fruits in the form of corn cobs enclosed by husks. There are two main types of corn harvesting, namely harvesting fodder corn or biomass using a combine harvester and harvesting grain corn using a combine harvester equipped with an appropriate front attachment. The forage harvester fragmentizes the entire corn plant (including the corn kernels), to permit the subsequent use thereof as fodder, in the form of corn for silage. In this fragmentized form, the corn plant also can be supplied as biomass to biogas plants. The forage harvesters used to harvest the corn plants process the entire corn plant, as explained previously, and therefore the fruit (i.e. the corn cobs comprising the corn kernels), do not need to be removed from the remaining plant components.
In contrast, in order to harvest grain corn using a combine harvester, the header thereof (which is used to harvest grain), is replaced by a front attachment for harvesting corn. This front attachment comprises a plurality of harvesting devices, namely intake conveyor mechanisms. Intake conveyor mechanisms grasp the particular corn stalk and guide the corn stalk within a guide track, via a picking device, which ensures controlled intake of the entire corn plant and removal of the corn cob from the corn stalk, and a cross conveyor, which draws the corn cobs separated from the individual corn stalks to the center of the front attachment (in the trough thereof), and transfers the corn cobs to a feed rake. The feed rake, however, is a component of the combine harvester. Consequently, when the front harvesting attachment is coupled to the combine harvester, the front harvesting attachment is connected to the feed rake, which feeds the corn cobs to a threshing mechanism of the combine harvester during the harvesting operation.
During the snapping procedure, the particular corn stalk pulled in the direction of the ground and, during this motion, is cut off close to the ground by means of optionally provided chopping knives of a chopping device (which are disposed on a vertically extending knife shaft), fragmentized and deposited on the field. It is also possible to provide a chopping device (in the form of a mulching device or a free-swinging mower), underneath the feed rake of the combine harvester or to mount the chopping device on the rear panel of the front attachment. The chopping device should ensure complete fragmentation of the corn straw, which comprises leaf portions of the corn plants and the corn stalks. Completely fragmented corn straw is distributed more uniformly over the ground and can be worked completely into the ground in subsequent soil management. Working the corn straw completely into the ground and mixing the corn straw uniformly with the ground in order to promote the rotting of the corn straw is of considerable importance for the prevention of pest contamination, such as contamination by fusarioses or Pyrausta nubilalis, for example.
As previously explained, a combine harvester can be equipped with entirely different front harvesting attachments, depending on whether grain or rapeseed or corn shall be harvested. The harvesting attachments are then coupled to the feed rake and to at least one driven mechanism of the combine harvester. The front harvesting attachments also differ in terms of the variability of the speeds for the harvesting devices to be provided within the front harvesting attachments. The speed of the picking rollers, for example, must be varied depending on the stand density, the stalk length and the moisture content of the corn. Corresponding means for performing such a speed adjustment of harvesting devices disposed on the front harvesting attachment are already provided on the combine harvester. If the combine harvester is used only to harvest grain (which is frequently the case), this speed adjustment for a front attachment for harvesting corn (which increases the production costs of the combine harvester), is entirely superfluous.
A front attachment for harvesting corn of the type is known from DE 10 2005 021 792 A1. This front attachment (which is referred to in this document as a picker), is detachably fastened to a feed rake of a combine harvester. A feed rake shaft of this feed rake is driven by the combine harvester by means of a chain drive and protrudes via one end beyond the lateral extension of a feed rake housing in a form of a shaft stub, which is connected to a universal drive shaft. This universal drive shaft is connected on the other side to an input shaft of a transmission. An output shaft of the transmission drives a cross conveyor by means of a pinion and a chain. A chain drive extends from the drive shaft of the cross conveyor and is used to drive a cross shaft of the snapping unit. This cross shaft comprises two bevel gears, via which shafts extending in the longitudinal direction of the front attachment drive pairs of snapping rollers (via three bevel gears in each case). The cross shaft further comprises devices for grasping and guiding the corn stalks.